FIG. 4.

SH2 domain of Stat5 required for activation by Jak2 but not by ΔJH2 or JH1. 293T cells were transfected with expression plasmids for Stat5 or SH2 mutant of Stat5 (mStat5). In addition, the cells were transfected with expression plasmids for Jak2-HA, ΔJH2-HA, or JH1-HA or left untransfected (—). Stat5 was immunoprecipitated (IP) with anti-Stat5 antibody. The immunoprecipitates were separated by SDS–7.5% PAGE and blotted with antiphosphotyrosine (anti-PY) or anti-Stat5 antibodies. Aliquots of cell lysates were analyzed by SDS–4 to 15% PAGE followed by anti-HA immunoblotting. The mobilities of the molecular mass markers (in kilodaltons) are shown on the left. Arrows on the right indicate the mobilities of the Jak2 proteins.